1. Field of the Invention
This invention relates to an automatic dispensing handheld caulking gun which is trigger activated and motor driven.
2. Description of the Related Art
Caulking guns which are designed primarily for dispensing prepackaged caulk held in containers or cylindrical cartridges are well known in the prior art. They are generally two types: manual and automatic dispensers. The manual type are widely used at present because of their cost advantage over automatic dispensers and because automatic dispensers today do not provide any real advantages over the manual type apart from the convenience of motor driven dispensed caulk.
Both manual and electrical caulking guns have in common a serious drawback which occurs when the user has completed the caulking task. The pressure applied to the cartridge remains after the task is completed unless the user releases the pressure manually. Even the most skilled artisan can not move quickly enough to avoid dispensing unwanted caulk which must be handled carefully and disposed of.
In the case of manual dispenser, pressure is applied axially along the cartridge as the trigger is pulled rearwardly. To release the axial pressure, the plunger must be manually disengaged from the trigger mechanism. This requires the user to change hands and to reposition the assembly, taking additional time and resulting in the discharge of unwanted caulk. Automatic or electric caulking guns have similar problems.
Alan B. Aronie and Joel Aronie attempted to resolve the problem of dispensing unwanted caulk using a quick pressure release drive means in U.S. Pat. No. 5,058,781. In that patent, the caulking material is dispensed by axial movement of an exterior threaded tube which is driven by a rotating ring gear interiorly threaded to mate with the tube. The tube is longitudinally split and is expandable/collapsible by a bushing within the tube. In the expanded position, the tube is engaged with the ring gear and axial pressure can be applied or maintained against the caulking cartridge. In the collapsed position, the tube is disengaged from the ring gear and axial pressure is released.
An external power source, such as an electric power drill, was used to drive the ring gear. Undesirable qualities, such as cost and bulk associated with power drills, became added features to the Aronie et al patent. Additionally, the means by which the power drill was attached to the caulking gun and the positioning of the power drill made the caulking gun unbalanced and cumbersome. To further complicate things, both hands were needed to efficiently operate the caulking gun: one hand to control the electrical operation of the gun and another hand to control the mechanical operation of repositioning the bushing within the tube to release the axial pressure.
The object of the present invention is to provide a caulking gun that releases pressure immediately from the caulking cartridge and addresses the design flaws in the Aronie patent with a novel plunger unit and triggering mechanism. Specifically, the present invention offers a quick release self-contained balanced handling caulking gun with a single triggering mechanism that controls both the mechanical and electrical aspects of the plunger unit.